1. Field of the Invention
The present invention relates to a personal digital assistant (PDA), and more particularly, to a PDA with a replaceable peripheral module at one of its corners.
2. Description of the Prior Art
In our modern information based society, the personal digital assistant (PDA) has become a requirement for most businessmen and people in the high technology field. Because the PDA has a vastly decreased size and power, many devices present in notebook computers are often omitted in embedded equipment of the PDA, causing the functionality of the PDA to be insufficient and inconvenient.
An add-on card with special functionality is a card that contains electronic devices and is inserted into an expansion slot formed in the PDA in order to improve its functionality. Recently, a common compact-flash (CF) card has been one of the add-on cardsused for improving the PDAs performance.
Please refer to FIG. 1, which is a schematic diagram of a prior art PDA 10 and an expansion slot 22. The PDA 10 includes a rectangular housing 14 having a touch screen 16 and a plurality of buttons 18 formed on the PDA 10. Users can touch the touch screen 16 and the buttons 18 to operate the PDA 10, and then the touch panel 16 displays pictures and characters to let the users read the pictures and characters. In order to hold an add-on card 12, the PDA 10 includes an insert opening 20 having the expansion slot 22 located in the insert opening 20. The add-on card 12 is covered with a rectangular case 24 having an opening 26 formed on a side of the rectangular case 24 and an interface connector (not shown in FIG. 1) corresponding to the expansion slot 22 located in the opening 26. When the add-on card 12 is inserted into the insert opening 20 of the PDA 10, the interface connector will be connected to the expansion slot 22, so that the add-on card 12 is connected to the PDA 10 for enhancing the PDAs functionality.
However, because the power supplied from the standard expansion slot of the CF card is limited, it limits the add-on cards functionality. In actual conditions, the highest current supplied from the standard expansion slot of the PDA is about 550 milliamperes (1 milliampere={fraction (1/1000)} ampere). If the add-on card needs more current to operate normally than the specification of the standard expansion slot of the PDA provides, the PDA cannot utilize this add-on card to improve its functionality. For example, a desired transient current of a radio frequency (RF) circuit for transmitting or receiving the RF signal operating in wireless communication is about 2000 milliamperes. Therefore, the RF circuit cannot be located in the add-on card due to the insufficient current of the slot, and the PDA cannot be improved in the field of the wireless communication by using the standard expansion slot of the CF card.
Further, the PDA usually has only one expansion socket due to the small size of the PDA. When the user wishes to operate multiple functions of the PDA simultaneously, it is inconvenient while using the PDA. For example, the embedded memory of the PDA contains 32 MB static random access memory (SRAM) and 16 MB flash memory in general. When the user utilizes a digital camera card to film images and process the images, the digital camera card has to be connected to the PDA to input the images. However, when occupied memory of the images become too large and the embedded memory of the PDA is insufficient, the memory of the PDA has to be expanded to satisfy the operation. That is, a memory card has to be inserted into the expansion slot of the PDA. However, the expansion slot already contains the digital camera card. Therefore, the images or information stored in the digital camera card has to be transferred via the PDA to an extra computer first, and then the images are processed and outputted by using the memory of the extra computer. However, this procedure causes great inconvenience for the user who operates the PDA.